1. Field of the Invention
The present invention relates, in a general way, to a sports boot, including for example, a gliding sport or other sport requiring the transmission of specific forces. More specifically, the present invention relates to a boot adapted to skiing on snow, ice skating, or skating on hard ground. In these cases, a gliding member is attached beneath the sole of the boot to transform it into an ice skate, a traditional roller skate, or an in-line roller skate.
2. Descrption of Background and Relevant Information
For boots of the aforementioned type, the external sole is made integral with the upper plate of a frame, on which the wheels are arranged, and from which an upper extends, covering the foot and extending in the direction of the skater's ankle.
One of the problems found in this type of boot lies in the fact that it is generally designed according to the techniques of alpine ski boots, i.e., having a one-piece shell made from a relatively rigid plastic material.
However, it has been observed, especially for in-line roller skating, that there is a decrease in shell rigidity caused by higher temperatures in this field of application, since this sport is practiced primarily in good weather. This phenomenon is accentuated further in regions with high temperatures.
This loss of shell rigidity is an essential criterion for the good transmission of forces and a good stability. Of course, it is possible to stiffen this shell in a general way, by making it from a material with a higher flexural modulus, but it would be at the expense of comfort and the enveloping qualities of the foot.
To overcome the aforementioned disadvantage, commonly owned French patent application No. 96.09054, and U.S. patent application No. 08/887,945, have proposed a sports boot in which the upper is composed of two parts, the first part being made from a relatively stiff material constituting a cradle, and the second part being made from a relatively flexible material constituting a vamp.
This construction allows for a compromise between the comfort and stiffness necessary in certain parts of the shoe.
Although such a design provides a solution to the above-cited problems, it in turn has the disadvantage of increasing the number of parts due to the fact that the upper is made of two parts.
Furthermore, it can be easily understood that it will be necessary to make two parts of different lengths for each boot size. Making such parts in plastic material calls for very expensive special tools.